Neuroprotective effects of Nigella sativa extract on cell death in hippocampal neurons following experimental global cerebral ischemia-reperfusion injury in rats

Background Global cerebral ischemia followed by reperfusion, leads to extensive neuronal damage, particularly the neurons in the hippocampal CA region. Recent studies have demonstrated that pharmacological agents, such as Nigella sativa L. (Ranunculaceae) that is an annual herbaceous flowering plant, given at the time of reperfusion afforded protection against ischemia, which is referred to as pharmacological post conditioning. Objectives The aim of this study was to evaluate the neuroprotective effects of Nigella sativa in the hippocampus neurons of rats exposed to global ischemia/reperfusion. Methods In the present study 30 Wister rats (200–250 g) were divided into 5 groups namely sham (operated without treatment), control (operation with normal saline treatment), and 3 treatment groups with Nigella sativa 1 mg/kg, 10 mg/kg and 50 mg/kg. Firstly, the animals were anesthetized by ketamin and xylazine, and then the right carotid artery was operated upon dissection of the soft tissues around it and ligation by a clamp for 20 min. The Nigella sativa extraction was used during surgery through IP route and after 72 h the animals were euthanized and their brain removed, fixed and prepared for histopathological examinations. Results In treatment group (1 mg/kg) the interstitial neuron frequency which contains cytoplasmic edema, along with CA, was 28 cells, whereas the edematous astrocyte number along with CA in this group was 115 cells. In the treatment group (10 mg/kg) the interstitial neurons of cornua ammonis (CA) were 15 and the edematous astrocytes were 122 cells and in the treatment group (50 mg/kg) the number of edematous interstitial neurons was 7 cells in distance of 2900 μ of CA. In such group the number of edematous interstitial neurons was less as well. In this group the appearance of CA cells was more similar to control group, not only the edema decreased in interstitial and astrocyte cells, but it dramatically decreased in pyramidal cells. Our study revealed that the Nigella sativa extraction could prevent intracellular edema of interneurons in 50 mg/kg group significantly compared to sham group (91.6%) and the extraction (50 mg/kg) decreased edematous astrocytes 67.1% dramatically compared to sham group. Furthermore there was no significant difference between control and two treatment groups (1 and 10 mg/kg) (P > 0.05), Conclusion Our finding suggested that the N. sativa extraction could prevent the cerebral edema which the best result was obtained in 50 mg/kg group; consequently such extraction is able to prevent ischemia/reperfusion in the hippocampus tissue of the brain.